Chapter 6

The XML Information Set (Infoset) and Beyond

6.1 Introduction

Look at any XML document and you will see a sequence of tags and values set out on a page or a computer screen. Zoom in (metaphorically) and it’s a sequence of characters. Zoom in again and it’s some ink on a page or pixels on a screen or bits in memory or on a disk. In whatever form the XML document is presented, that form represents some information – the cast of a movie, the line items in a purchase order, or the sections and chapters of this book. When a program performs operations on XML – query, update, extract – it does not need or want to deal with bits in memory or even with tags and values. The program wants to operate on the information itself.

To that end, the ...

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